A variety of different physiological characteristics are monitored for many different applications. For instance, physiological monitoring instruments are often used to measure a number of patient vital signs, including blood oxygen level, body temperature, respiration rate and electrical activity for electrocardiogram (ECG) or electroencephalogram (EEG) measurements. For ECG measurements, a number of electrocardiograph leads may be connected to a patient's skin, and are used to obtain a signal from the patient.
Obtaining physiological signals can often require specialty equipment and intervention with medical professionals. For many applications, such requirements may be costly or burdensome. These and other matters have presented challenges to monitoring physiological characteristics.